Although engine painting mostly serves aesthetic purposes, it also has practical benefits. To achieve a long-lasting paint job, you need properly-cured engine enamel paint. So how do you cure this type of paint? We've done the research for your convenience.
Engine enamel paint cures on its own after five to seven days of application. But you need to leave the paint untouched and unexposed to dirt, moisture, and the outdoor environment in general. You can also speed up curing through a few methods, namely:
- Convection curing
- Infrared curing
- UV curing
- Electron-beam processing
Would you like to know more about engine enamel painting and curing? Keep reading as we've prepared some interesting tips and tidbits for you.
How Long Does Engine Enamel Take To Cure?
Engines normally operate between 167 to 221 degrees Fahrenheit (75 to 105 degrees Celsius). In addition to this, turbochargers and other engine technologies can raise the temperature under the hood up to 392 degrees Fahrenheit (200 degrees Celsius).
With the engine's extreme operating conditions, you can't coat it with just any type of metal paint. For example, standard polyurethane paint can only withstand up to 200 degrees Fahrenheit (93 degrees Celsius).
Many engine enamel paint products have been engineered to resist temperatures of about 500 degrees Fahrenheit (260 degrees Celsius). Some special enamel products can even withstand up to 2,000 degrees Fahrenheit (1,093 degrees Celsius).
Moreover, some modern engine enamel products have ceramic resins that produce a hard and glossy finish with great color retention. This type of paint will hold strong in conditions that can make normal car body paint peel off or even evaporate into fumes.
For the enamel to achieve the best finish, you need to let it cure properly. Enamel paint cures on its own, but you must leave the paint untouched and free from dirt and moisture during its curing period.
Can I Speed Up Paint Curing?
Most engine enamel paint products provide instructions only for the normal week-long curing process, although there are some methods to speed up the paint curing time.
In general, you can accelerate paint curing time by increasing temperature and decreasing humidity. Certain technologies can also speed up the process using electrons and ultraviolet (UV) light.
Convection curing is the most simple way to accelerate paint curing, as it simply involves heat transfer around the painted surface.
Some automotive paint experts "bake" the painted metal in a large oven after the paint becomes dry to handle. They recommend a temperature of 200 degrees Fahrenheit (93 degrees Celsius) for 20 minutes.
Alternatively, some engine paint professionals also recommend using the normal engine heat to speed up curing. If you painted the engine while it was in the car, you can start it up and let it run for 20 minutes as well.
You may also do a little DIY to convert a garage section into a temporary paint booth for your engine paint's curing.
You may use a fan or dehumidifier to decrease air humidity in the booth. Additionally, you can use your home's heater or a heating lamp to raise the temperature.
UV rays can speed up the engine paint curing time from days to minutes. Of course, this specific curing time can vary depending on the paint type, painted area, and coating thickness.
Check this video on how a UV paint-curing product can cure a small section of automotive body paint in just 1 minute:
Although UV rays do not use heat to cure paint, they can cause serious damage to your eyes. When using a UV paint curing product, always make sure that you use the proper protective gear.
Unlike UV light curing, infrared curing involves heat. Using infrared heating lamps, you can also reduce your paint curing time to several minutes.
Electron Beam Processing
Electron Beam (EB) curing is an industrial process for curing high-performance product coatings. Whereas UV curing involves light radiation, EB curing uses electron energy to speed up the paint curing process.
Unfortunately, EB paint curing is not as commercially-available as UV or infrared curing products.
Why Does Paint Need To Cure?
Curing is the process that paint undergoes to reach its maximum hardness. If exposed to even mild pressure, impact, or the outside environment, uncured enamel paint can wrinkle, peel off, or chip from the painted surface.
Engine enamel especially needs to cure completely as it needs to reach its maximum adhesion, durability, and heat resistance before it gets subjected to harsh conditions under the hood.
What Is The Difference Between Curing And Drying?
Some people confuse paint curing with paint drying. But you should be careful to distinguish one from the other, especially as this confusion can lead to ruined paint jobs and wasted time, effort, and resources.
Paint is "dry" when enough of its solvents (e.g., oil or water) evaporate from the applied paint. After application, some engine enamels become dry to the touch after 20 minutes, and dry to handle and recoating after 1 hour.
On the other hand, paint is "cured" when its pigments turn from liquid to solid, and the compound reaches maximum bond strength and hardness. As mentioned above, this process takes about a week for engine enamel.
How Do You Paint An Engine At Home?
If you want to paint your engine in the comfort of your own home, then you need to remember four important aspects of good paint jobs.
1. Surface Preparation
Surface preparation is possibly more complicated and tedious than the painting job itself. You need to do the preparation steps properly to make sure that your paint job will be successful.
- Cleaning and degreasing - Use mild detergent and degreasers to remove grease, dirt, and other contaminants. You may clean and degrease with brushes and abrasives. You may also use a hot tank, as shown in the video below.
- Rust removal - Use a power sander, wire brush, or sandpaper to remove surface rust. You may also need to repair any holes on the surface.
- Paint stripping - Use a paint stripper to remove old engine paint. If the old paint is still in good condition, you can sand the surface for the new primer to bond properly.
- Cleaning and drying - Make sure that the surface is completely dry. You may use acetone or an air compressor to speed up the drying. Some car paint experts use an oven or a gas torch to help the moisture evaporate.
2. Surface Etching
Some modern primer products are self-etching. You can still use fine sandpaper or a power tool with a 320 to 400-grit attachment, though, to ensure better primer adhesion. Make sure to clean and dry the surface again after etching.
3. Taping Or Masking
Use tape or other masking material to cover the engine's cylinder bores, crankshaft, pistons, and other parts that should not get painted.
4. Primer Coating
Start your primer application as soon as you finish the preparation steps because all the abrasive products have removed any previous protective coatings of the engine surface.
Apply two to three coats of high-temperature, heat-resistant enamel primer for your engine.
Painting The Whole Engine
Many automotive paint experts say that proper engine painting can only be done while the engine is out of the car. After all, you need to clean, tape, and coat even the lower parts of the engine. You surely don't want to paint on other parts inside the engine bay.
Here's a helpful video on how to paint an engine that's out of the car:
Painting Parts Of The Engine
Not many car owners have the tools, resources, and expertise to pull the engine out from under the hood. This process needs to be done in a well-equipped garage or a professional auto repair shop.
Instead of taking the whole engine out, some weekend DIYers may be contented to dismantle and paint the highly visible engine parts.
Here's a great video on how you can paint some engine parts while leaving the engine in the car:
How Do You Apply Enamel To Metal?
Many of today's engine enamel products come in convenient aerosol "rattle cans." Hence, we've listed down some tips on how to spray-paint your engine surface properly:
- Shake the can well and make a few test sprays away from the project's surface.
- Always spray with long and sweeping motions to get even paint coats.
- Keep the spray can at a constant distance with every pass.
- Make sure to overlap each pass by approximately 50% to ensure complete paint coverage.
- More thin coats will give a better finish than fewer thick coats.
Should I Paint My Engine?
Some car owners paint their engines for restoration and surface protection purposes. Other enthusiasts, in turn, paint their engines for purely aesthetic purposes.
Finally, some performance-oriented drivers paint their engines black for slightly better engine cooling. Based on scientific studies, black radiates heat (or cools down) faster than other colors.
Painting your engine has practical and aesthetic benefits. Either way, you should weigh if the benefits are worth the time, effort, and resources that you need for such a project.
Engine enamel paint normally takes about a week to cure after application. However, you can speed this process up through convection, infrared, UV, or electron-beam curing.
We hope we have helped you understand how to cure your engine's new enamel paint.
For more interesting reads about automotive paints and other car topics, you may also check out these great articles below.